1. Technical Field
Exemplary aspects of the present invention relate to an image forming apparatus and an image forming method, and more particularly, to adjustment of an output value of a charging bias based on a toner adhesion amount of each area in a movement direction of a background fog pattern formed on a surface of a latent image bearing member, and an image forming apparatus implementing the adjustment.
2. Related Art
Conventionally, image forming apparatuses that form an image using an electrophotographic process are known.
In such an image forming apparatus, a charging device uniformly charges a surface of a photosensitive member serving as a latent image bearing member. Meanwhile, the surface of the photosensitive member, having passed a charge position opposite the charging device, is irradiated by an optical scanner, thereby forming an electrostatic latent image on the surface of the photosensitive member that is conveyed to a development position opposite a development device, which develops the electrostatic latent image into a toner image. Subsequently, the toner image on the surface of the photosensitive member is conveyed to a transfer position opposite a transfer unit that transfers the toner image to a recording sheet directly or via an intermediate transfer member.
In such an, electrophotographic process, a charging bias to be supplied to the charging device is controlled to be constant. However, such straightforward control cannot maintain a constant electric potential of a background area on the surface of the photosensitive member for long because the potential of the background area changes with changes in the environment (e.g., temperature and humidity), changes in electrical resistance of a charging member (e.g., a charging roller) in the charging device over time, and changes in thickness (e.g., abrasion) of a surface layer of the photosensitive member.
The change in the potential of the background area may cause various problems due to excessive or insufficient background potential that is the difference between the potential of the background area and the potential of a development member (e.g., a development roller) of a development device. For example, insufficient background potential may cause background fogging due to transfer of toner on the development member to the background area on the surface of the photosensitive member. Moreover, in an image forming apparatus employing a two-component development method that uses a two-component developer containing toner and magnetic carrier as a developer, excessive background potential may cause a phenomenon called carrier adhesion, in which the magnetic carrier on a development member is transferred to a surface of a photosensitive member.